uric acid

(yo͝or`ĭk), white, odorless, tasteless crystalline substance formed as a result of purinepurine,
type of organic base found in the nucleotides and nucleic acids of plant and animal tissue. The German chemist Emil Fischer did much of the basic work on purines and introduced the term into the chemical literature in the early 20th cent.
..... Click the link for more information. degradation in man, other primates, dalmatians, birds, snakes, and lizards. The last three groups of animals also channel all amino acidamino acid
, any one of a class of simple organic compounds containing carbon, hydrogen, oxygen, nitrogen, and in certain cases sulfur. These compounds are the building blocks of proteins.
..... Click the link for more information. degradation into the formation of glycineglycine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Glycine is the only one of these amino acids that is not optically active, i.e., it does not have d- and
..... Click the link for more information. , aspartic acidaspartic acid
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer participates in the biosynthesis of proteins.
..... Click the link for more information. , and glutamineglutamine
, organic compound, one of the 20 amino acids commonly found in animal proteins. Only the l-stereoisomer occurs in mammalian protein.
..... Click the link for more information. , which combine to form purines and finally uric acid; these so-called uricotelic organisms thus excrete uric acid as the major end-product of the metabolism of all nitrogen-containing compounds. Uric acid is a very weak organic acid that is barely soluble in water and insoluble in alcohol and ether. The urates are its salts. Uric acid is present in human urine only in extremely small amounts but constitutes a large part of the body waste matter of birds (see guanoguano
, dried excrement of sea birds and bats found principally on the coastal islands of Peru, Africa, Chile, and the West Indies. It contains about 6% phosphorus, 9% nitrogen, 2% potassium, and moisture. Guano is found mixed with feathers and bones and is used as a fertilizer.
..... Click the link for more information. ) and of reptiles. It collects sometimes in the human kidneys or bladder in calculi, or stones, and is responsible, when present in tissues or deposited upon bones in the form of urates, for gouty conditions (see goutgout,
condition that manifests itself as recurrent attacks of acute arthritis, which may become chronic and deforming. It results from deposits of uric acid crystals in connective tissue or joints.
..... Click the link for more information. ). It occurs also in normal human blood. The pure acid is obtained from guano and other similar substances. Upon decomposition urea is obtained. A common test for the presence of the acid in urine depends upon the formation of murexide (an ammonium salt), which is an intense reddish purple. Nitric acid is added to the urine, which is then evaporated. If uric acid is present, murexide is formed when ammonia is added to the residue.

Uric acid

The main excretory end product of protein metabolism in certain species of birds and reptiles. In mammals, uric acid is derived from purines; in higher primates, including humans, it is excreted as such and is not oxidized to allantoin, the main excretory purine metabolism product of most species. In humans, uric acid levels are increased following excessive intake of dietary purines, primary synthesis in certain diseases (gout, Lesch-Nyhan syndrome), endogenous nucleic acid metabolism (leukemia, an abnormal number of erythrocytes in blood, chemotherapy-induced tumor lysis), and restricted renal excretion (renal diseases, ketoacidosis, lacticidosis, diuretics). Uric acid levels are lowered by the use of drugs causing increased uric acid excretion, and by renal tubular defects. See Liver, Nucleic acid, Protein metabolism, Purine

Uric Acid

(2,6,8-trioxypurine), a colorless, crystalline solid that is very slightly soluble in water and that decomposes below the melting point. Uric acid, which was discovered in 1776 by K. Scheele as a component of urine, can exist in two forms— keto and enol:

In man and primates, uric acid is the end product of purine metabolism, forming as a result of the enzymatic oxidation of xanthine; in all other mammals, uric acid is converted into allantoin. The brain, liver, and blood of all mammals and man, as well as the urine and sweat, contain small quantities of uric acid. Some metabolic disorders are characterized by an accumulation in the body of uric acid and of uric acid salts (called urates); gouty deposits and the formation of stones in the kidneys and urinary bladder often accompany these metabolic disorders.

In birds, some reptiles, and most terrestrial insects, uric acid is the end product not only of purine metabolism but also of protein metabolism. Because an organism requires only a minimal amount of water in order to eliminate uric acid from the body (uric acid can even be eliminated as a solid), these animals, which have a limited water balance, use the uric acid biosynthetic pathway as the primary mechanism for neutralizing ammonia. (The neutralization is advantageous because ammonia is a more toxic product of nitrogen metabolism than uric acid.) This mechanism is in contrast to the mechanism found in most vertebrates, which have a more complete water balance and thus use the urea biosynthetic pathway as a means of neutralizing ammonia. (Urea requires much water to be safely eliminated from the body.)

Up to 25 percent of avian excrement, or guano, is uric acid; thus, the excrement serves as a source for obtaining uric acid. Uric acid is also found in a number of plants. It is the starting material for the synthesis of caffeine.

REFERENCES

Prosser, C. L., and F. Brown. Sravnitel’naia fiziologiia zhivotnykh. Moscow, 1967. (Translated from English.)

E. N. SAFONOVA

uric acid

[′yu̇r·ik ′as·əd] (biochemistry) C₅H₄N₄O₃ A white, crystalline compound, the excretory end product in amino acid metabolism by uricotelic species.

uric acid

a white odourless tasteless crystalline product of protein metabolism, present in the blood and urine; 2,6,8-trihydroxypurine. Formula: C₅H₄N₄O₃

uric acid

uric

[u´rik] urinary.uric acid the end product of purine metabolism or oxidation in the body. It is present in blood in a concentration of about 5 mg/100 ml and is excreted in the urine in amounts of a little less than 1 g per day. In gout there is an excess of uric acid in the blood, and its salts, the urates, form insoluble stones in the urinary tract, or may crystallize and form deposits (see tophus) in the joints and tissues. The presence of high concentrations of uric acid in the urine is significant in the diagnosis of gout, but is of little significance in urinary disorders.

u·ric ac·id

(yūr'ik as'id), 2,6,8-Trioxypurine; white crystals, poorly soluble, contained in solution in the urine of mammals and in solid form in the urine of birds and reptiles; sometimes solidified in small masses as stones or crystals or in larger concretions as calculi; with sodium and other bases it forms urates; elevated levels associated with gout. Synonym(s): lithic acid, triketopurine

uric acid

n. A semisolid compound, C₅H₄N₄O₃, that is a nitrogenous end product of protein and purine metabolism and is the chief nitrogenous component of the urine in birds, terrestrial reptiles, and insects.

uric acid

A small purine metabolite excreted primarily by the kidneys, less by the GI tract; ↑ UA occurs in gout, which primarly affects acral joints, associated with deposition of UA crystals in various tissues; ↑ UA occurs in rapid cell turnover–eg, cancer–leukemia, metastases, myeloma, as well as in alcoholism, dehydration due to diuretics, DM, hyperlipoproteinemia, lead poisoning, renal failure, rarely, idiopathic Ref range Serum, ♂, 3.6-8.3 mg/dL; ♀, 2.2-6.8 mg/dL. See Gout. Cf Synovial fluid analysis.

CLUMP OF URIC ACID CRYSTALS (×400)

uric acid

C₅H₄N₄O₃, a crystalline acid occurring as an end product of purine metabolism. It is formed from purine bases derived from nucleic acids (DNA and RNA). It is a common constituent of urinary stones and gouty tophi. See: illustrationCAS # 69-93-2

Output

Uric acid must be excreted because it cannot be metabolized. Uric acid output should be between 0.8 and 1g/day if the patient is on an ordinary diet.

Increased elimination is observed after ingestion of proteins and nitrogenous foods, after exercise, after administration of cytotoxic agents, and in gout and leukemia. Decreased elimination is observed in kidney failure, lead poisoning, and in those who eat a protein-free diet.

uric acid

The main end product of PURINE metabolism. Uric acid is derived from ADENINE and GUANINE, two of the purines in DNA and RNA (nucleic acids). An excess of uric acid salts in the body can cause GOUT and kidney stones.

uric acid

see URATE.

Uric acid

A compound resulting from the body's breakdown of purine. It is normally present in human urine only in small amounts.Mentioned in: Uric Acid Tests

u·ric ac·id

(yūr'ik as'id) White crystals, poorly soluble, contained in solution in the urine of mammals.

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Uric Acid

REFERENCES

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uric

u·ric ac·id

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Output

uric acid

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Uric acid

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Words related to uric acid

noun a white tasteless odorless crystalline product of protein metabolism

Related Words